Fatty acid biosynthesis (or Fab) is an essential metabolic process for all living organisms. It is used to synthesize the metabolic precursors for membrane phospholipids in the cell wall. Fatty acids are synthesized by mammals (using enzyme FAS I) and bacteria (using enzyme FAS II) via substantially different biosynthetic mechanisms, thus providing the possibility of bacteria-specific drug targeting. Indeed, inhibitors targeting the various stages of the fatty acid biosynthetic pathway have been investigated as novel anti-bacterial agents. Broadly, the pathway of saturated fatty acid biosynthesis (FAB) is more or less similar in all organisms, however, the fatty acid synthase (FAS) enzymatic biosynthesis systems vary considerably with respect to their structural organization. Mammalian fatty acid synthesis (FAS-I) employs a multifunctional enzyme complex in which all enzymatic activities reside on a single polypeptide. In contrast, bacterial fatty acid synthesis (FAS-II) elongation cycle utilizes several distinct monofunctional enzymes with activity pertaining to respective enzyme peptides effecting fatty acid chain elongation and ultimately cell membrane production. Enoyl acyl carrier protein reductase (FabI) is the component of FAS-II that catalyzes the final reaction in the enzymatic sequence. Hence, there appears to be considerable scope for the selective inhibition of the bacterial FAS system enzymes by exploring newer anti-bacterial agents.
Fab I (a protein enzyme encoded by EnVM gene) acts as an enoyl-ACP reductase (Bergler, et al, (1994), J. Biol. Chem. 269, 5493-5496) in the final step of the reactions involved in each cycle of bacterial fatty acid biosynthesis. Further rounds of this cycle, adding two carbon atoms per cycle, eventually lead to palmitoyl-ACP (16-Carbon), and subsequently the cycle is blocked largely due to feedback inhibition of Fab I by palmitoyl-ACP (Heath, et al, (1996), J. Biol. Chem. 271, 1833-1836).

Thus, Fab I is among one of the major biosynthetic enzyme and appears to be a key moderator in the overall bacterial fatty acid biosynthetic pathway. Therefore, Fab I may be one of the meaningful target for acquiring anti-bacterial role.
Though there is plethora of literature on Fab I, which provides different inhibitors, however, among promising literature, it reveals that diazaborine (an antibiotic) inhibit fatty acid, phospholipid and lipopolysaccharide (LPS) biosynthesis via Fab I as one of the anti-bacterial target. Grassberger, et at in J. Med Chem 27, 947-953 (1984) reported derivative of 2b18 (a peptide) possessing non-competitive inhibitory activity of Fab I (Bergler, et al, (1994) J. Biol. Chem. 269, 5493-5496). Bergler et al in J. Biol. Chem. 269, 5493-5496 (1994) reported that inhibition of Fab I either by diazaborine or by raising the temperature in a Fab I temperature sensitive mutant is lethal. These results demonstrate that Fab I appears to be essential for the survival of the organism. McMurry et at in Nature 394, 531-532 (1998) have shown that Fab I is also the target for the well known broad spectrum anti-bacterial agent triclosan. Recent literature including U.S. Pat. Nos. 7,790,716; 7,741,339; 7,557,125; 7,524,843; 7,250,424; 7,049,310; 6,846,819; 6,765,005; 6,762,201; 6,730,684 and 6,503,903 also reveals that diverse compounds are known to possess Fab I inhibitory activity and have anti-bacterial role, and, therefore, may be useful for the treatment of bacterial infections in mammals, particularly in man.
Further various antimicrobial resistances among clinical isolates have been observed as one of the major problem in recent years. Of particular concern has been the increasing incidence of methicillin-resistant Staphylococcus spp., vancomycin-resistant Enterococcus spp., and penicillin-resistant Streptococcus pneumoniae. 
Despite various disclosures on Fab I inhibitors, however, with the rise in number of patients affected by diverse bacterial and related microbial diseases and drug resistance, there appears to be unmet need for newer drugs that can treat such diseases more effectively. There is still need for newer anti-bacterial agentswhich may be further useful in a wide variety of bacterial infections and possessing broader spectrum.